The aim of the proposed series of studies is to understand the organization of color processing in the primate visual cortex in terms of the underlying circuitry and connectivity. The project will exploit the combination of standard electrophysiological and anatomical techniques with a recent technical innovation: optical recording of cortical activity. This combined approach will first be used to identify the color selective regions of V1 and V2, and then to reveal the subset of those regions coding for one particular color or another (e.g. one region may code for red vs green color opponency and another for blue vs. yellow). Although electrophysiological evidence suggest that such a segregation exists in V1, its distribution over the cortex on a larger scale and its dependency on eccentricity are unknown. Whether there exist regions within the thin stripes of V2 that are dedicated to one color opponency is also uncertain. The combination of conventional techniques with in vivo optical recording of color selectivity should clarify these issues. In addition to studying the functional organization of color processing in visual cortex, another major aim of this project is to further our understanding of the neuronal circuitry and connectivity that is responsible for color processing. It is well known that the sophistication of the receptive field properties of visual cortical cells (both color and non-color) progresses as one examines each successive stage in visual processing. By studying the relationship between the receptive field properties of color cells at several cortical stages, and the connections that these cells make, we will be able to better understand how thee cells contribute to color processing as well as general principles in neural circuitry. These experiments will also provide an opportunity to quantify the receptive field size, overlap and scatter of the color selective cells which will help answer questions concerning coverage and visual acuity afforded by the color system at the cortical level. The optical recording maps will provide a powerful tool to guide these studies by directing the precise placement of electrodes and tracer injections in the color regions of interest.